1. Field of the Invention
The present invention relates to a sputtering device, and in particular to a sputtering device which allows a film to be formed on a substrate by means of the simultaneous sputtering of a plurality of targets, so as to economize on space and achieve a higher throughput.
2. Description of Related Art
In the usual conventional sputtering device, a film is formed on a substrate by means of the sputtering of a target of a size allowing a film to be formed on the surface of a substrate where the intended film is to be formed.
FIG. 1, which is a schematic for illustrating the primary components in the sputtering process chamber (referred to as the sputtering chamber) of such a conventional sputtering device, is a plan that is viewed from above parallel to the substrate surface. 100 is a tray, 102 is a gate valve, and 104 are substrates mounted on the tray. As is well known, the substrates 104 are fed in and out in the direction indicated by arrow a through the gate valve 102 into the sputtering chamber.
110 are cathodes with cathode mounting surfaces parallel to the substrate surface, and 112 are targets mounted on the cathode mounting surfaces.
The targets 112 are usually of a size greater than the size of the substrate. In a conventional sputtering chamber, the film is formed with the target disposed in a position suitable for forming the film, one target per substrate. Accordingly, in cases where films are sequentially built up on a substrate using different types of targets, dedicated sputtering chambers of the same type as the type of target are prepared, and the films are formed in sequence in the various different sputtering chambers.
Thus, in conventional sputtering devices, a dedicated sputtering chamber is required for each different type of target, unavoidably resulting in a device of large size, and the need for moving the substrate in and out of each sputtering chamber and other related operations result in a lower throughput.
Furthermore, in conventional devices, increases in the substrate size are accompanied by increases in the size of the target, making it difficult to form a film of uniform thickness on surfaces of large area where the film is to be formed. It is thus difficult to achieve the film thickness distribution standards required of film-forming devices when using conventional sputtering devices.
Japanese Examined Patent Application (Kokoku) 8-26453 discloses a sputtering device in which a plurality of targets are provided to form an alloy thin film. In this sputtering device, three cathodes are provided in one sputtering chamber, where one target of a certain type is attached to the center cathode, and the targets attached to the remaining two cathodes are different from the center target but are the same as each other. In this conventional example, it is disclosed that the center target is disposed parallel to the surface of the substrate on which the film is formed, that the two flanking targets are disposed at an incline, and that the distance between the targets and the surface on which the film is to be formed, as well as the incline of the two flanking targets, can be adjusted.
However, because the device disclosed in Japanese Examined Patent Application (Kokoku) 8-26453 is a device for forming a single alloy film with a composition consisting of the target components, that is, the alloy components, it is necessary to move the substrate in and out of separate sputtering chambers to form different types of films continuously on the alloy film. Naturally, the problems of economizing on space and achieving a higher throughput described in the present application are therefore not solved by this device.
Japanese Unexamined Patent Application (Kokai) 6-122971 discloses a sputtering device in which a plurality of targets is provided to form a film consisting of a plurality of constituent elements. In this sputtering device, a plurality of targets are sequentially passed through sputtering positions, and each time a film component is formed, it is formed while a target is facing the substrate.
However, since even the device disclosed in Japanese Unexamined Patent Application (Kokai) 6-122971 is a structure in which the substrate and target are aligned in a one-to-one relation when the film is formed, the aforementioned problems naturally remain unsolved.
An object of the present invention is thus to provide a sputtering device which allows a film to be formed on a substrate by means of the simultaneous sputtering of a plurality of targets, so as to economize on space and achieve a higher throughput.
To achieve this object, the sputtering device of the present invention comprises the following structural features.
That is, the sputtering device comprises a sputtering chamber, a plurality of target supports, cathodes, and a target-positioning mechanism.
The plurality of supports are provided apart from each other in the sputtering chamber. The supports are provided in such a way that the target-mounting surfaces are aligned facing the film-forming surface of the substrate mounted on a substrate holder or tray. Each of the supports is also constructed in such a way as to be able to rotate (or turn) around the center axis.
Each support is provided with cathodes. The plurality of cathodes provided on a support are provided apart from each other, each cathode having a plurality of target-mounting surfaces.
The target-positioning mechanism is able to rotate the supports having targets mounted on their target-mounting surfaces, so as to position one of the plurality of targets on each support into film-forming position where the target faces the surface where the film is to be formed.
Thus, in the structure of the sputtering device of the invention, the supports are provide facing the surface of the substrate on which the film is to be formed. The supports are provided with an equal number of a plurality of cathodes. Targets that are different from each other can be mounted on the target-mounting surfaces of the plurality of cathodes per support. When a plurality of kinds of targets are mounted on each support, the same number of kinds, preferably in the same order, are provided.
Because targets of the same type can thus be mounted on each support, the same kinds of targets, which are divided across several small targets, can be mounted instead of using a single large-sized target, so as to form a film of more uniform thickness on a substrate shared in common. Particularly when the substrate is a glass substrate, the greater the size of the glass substrate the more beneficial it is, in the interests of making a more uniform film thickness, to produce a film with a plurality of targets with a surface area equal to a small-sized glass substrate.
Because the structure of the present invention also permits a plurality of targets to be provided per support, as described above, the targets can be arranged in such a way that the types of targets provided on each support are the same, so that the supports can be rotated by the target-positioning mechanism to select and position targets in order to produce a film with different components. It is thus possible to continuously produce a film with two or more different components on the same substrate in the same sputtering chamber. Thus, even though it was conventionally necessary to provide a sputtering chamber for each type of target, in the present invention it is possible to use a single sputtering chamber, that is, film-forming chamber, to form a plurality of films using different targets.
Thus, because there is no need for moving the substrate in and out of different sputtering chambers for each component of a film or other related operations, the device of the invention results in smaller space and higher throughput than in conventional devices.
Because targets of a small size are used, not targets of a large size, the unit cost of the targets is less expensive, resulting in lower overall costs.
Furthermore, because the supports themselves in the sputtering device of the present invention are constructed in the form of rotatable supports, the targets can be pre-cleaned as desired on the surfaces of the targets, which are the surfaces not facing the substrate, making it possible to smooth areas which are not erosion regions, eliminate splats, and eliminate nitride films formed on target surfaces in the case of Ti targets, for example.
When working the invention, the center target-mounting surface facing the center of the surface on which the film is to be formed should be parallel to that surface. Even more preferably, the peripheral target-mounting surfaces on the periphery of the surface on which the film is to be formed should be inclined relative to the center target-mounting surface in such a way that the sides which are further away from the center target-mounting surface are closer to the surface on which the film is formed.
The angle of incline of the center and peripheral target surfaces relative to the surface on which the film is formed can thus be varied to allow a film of more uniform thickness to be formed.
When rotating the supports themselves to position the peripheral targets, the angle of rotation can be selected to adjust the angle of incline (also called inclination) of the target-mounting surface relative to the surface on which the film is formed, and thus of the target surface. Because the film-forming conditions are different in the initial stages of sputtering than at the target life end, the angle of inclination of the peripheral target surfaces can be adjusted to ensure that the film is formed as befits the various stages. If necessary, the supports can also be rotated (rotated and oscillated) within a certain range of angles of rotation to produce a film while allowing the angle of inclination to vacillate within a certain range.
The conditions should be experimentally checked in advance for the angle of inclination of each type of target that is used so as to adjust the angle of inclination of the peripheral targets to certain suitable angles under the prescribed conditions. In some cases, it is possible to form an optimal film by adjusting the angle during the formation of the film.
In a preferred sputtering device of the invention, the center axes of the supports serve as the rotating shafts of the supports, each rotating shaft being parallel to each other and to the surface on which the film is to be formed, and/or a plurality of supports is aligned in the direction in which the substrate holder or tray is moved in and out. Such a target-positioning mechanism will have a simpler structure.
The sputtering device of the present invention should also be provided with a distance-adjusting mechanism for adjusting the distance between the surface on which the film is to be formed and the sputtering surfaces of the targets mounted on the target-mounting surfaces, and/or the distance between the central axes of the various supports.
This will allow films of more uniform thickness to be formed according to the film-forming conditions. The conditions for such distance relationships should be experimentally checked in advance for each type of target so as to allow the distance to be set to a certain suitable distance under the prescribed conditions. In some cases, it is possible to form an optimal film by adjusting the distance during the formation of the film.
Each support of the sputtering device of the present invention should preferably be provided with a shield (also referred to as adhesion-preventing jig) in the sputtering chamber so as to encompass the support along a portion of the periphery of the support but not encompass the target facing the substrate when the film is formed. In this case, a shield-driving mechanism should be provided for driving the shield in conjunction with or independently of the supports.
Such a shield can be provided to align the targets into position so as to ensure that the sputtering surface of the target to be sputtered faces the substrate during the formation of the film, and also to protect targets that are not being used in the sputtering from scattered particles or sputter atoms produced during the sputtering process. Not only does this shorten the time needed for cleaning, but it also reduces the number of cleanings.
The sputtering device of the present invention may be a double-sided film-forming type of device. The cross section shape of the supports may be any one selected from polygonal shapes such as triangular, tetragonal, pentagonal or other polygonal more than pentagonal shapes, according to the number of targets that are used in the same sputtering chamber and that are mounted on a single support. Doing this will allow different types of targets to be mounted, in the maximum number corresponding to the number of sides (surfaces) of the support, on each support, and will thus allow the number of films corresponding to that number, and more films in the case of Ti films, TiN films obtained by reactive sputtering, or the like, to be built up on a substrate.
The substrate on which the film is formed by the sputtering device of the present invention should be a glass substrate, and such a glass substrate should preferably be larger than a semiconductor silicon wafer.